All of the blood in your body travels through your heart about once a minute.
 
Your heart is an efficient machine with a specialized set of working parts. Learn what these parts are, and how they work together, by reading below.
 
Parts of the Heart
 
Taking Sides
Your heart is divided into two sides—right and left. A thick wall of tissue called the septum separates the right and left sides.
 
The right side of a heart usually appears to the left in diagrams, and the left side on the right.
 
Chambers
Your heart is divided into four chambers: the right atrium, right ventricle, left atrium, and left ventricle.
 
The atria are your heart’s upper chambers. They collect blood as it flows into the heart.
 
The ventricles are your heart’s lower chambers. They pump blood from the heart to the rest of the body.
 
Valves
Your heart has four valves. These valves only open in one direction, to prevent blood from flowing backward. Valves control the flow of blood from the atria to the ventricles, and from the ventricles to the rest of the body. 
 
Your tricuspid valve controls the flow of oxygen-poor blood from the right atrium to the right ventricle. 
 
Your pulmonary valve controls the flow of blood from the right ventricle to the pulmonary artery, which carries blood from your heart to your lungs.
 
Your mitral valve controls the flow of oxygen-rich blood from the left atrium to the left ventricle.
 
Your aortic valve controls the flow of blood from the left ventricle to the rest of your body.
 
Arteries
Arteries are blood vessels that transport blood from the heart to the body. Your heart has two major arteries and several coronary arteries.
 
Your pulmonary artery carries oxygen-poor blood from the right ventricle of your heart to your lungs, where it is oxygenated as you breathe in.
 
Your aorta carries oxygen-rich blood from the left ventricle of your heart to the rest of your body.
 
Your coronary arteries branch off from the aorta to carry oxygen-rich blood to the myocardium—the heart muscle itself.
 
Veins
Veins are blood vessels that carry blood from the body to the heart. Your heart has six major veins.
 
The superior vena cava carries oxygen-poor blood from the upper body to the right atrium.
 
The inferior vena cava carries oxygen-poor blood from the lower half of the body to the right atrium.
 
Four pulmonary veins carry oxygen-rich blood from the lungs to the left atrium.
 
Going with the Flow
 
1. Oxygen-poor blood flows into the right atrium from the vena cavae (superior and inferior vena cava).
 
2. Blood is pumped through the tricuspid valve from the right atrium to the right ventricle.
 
3. Blood is pumped through the pulmonary valve from the right ventricle to the pulmonary artery.
 
4. Blood flows through the pulmonary artery to the lungs.
 
5. Oxygenated blood flows from the lungs to the pulmonary veins.
 
6. Blood flows from the pulmonary veins to the left atrium.
 
7. Blood is pumped through the mitral valve from the left atrium to the left ventricle.
 
8. Blood is pumped through the aortic valve to the aorta, coronary arteries, and the rest of the body.
  1. What makes your pulmonary veins different from almost every other vein in your body?

    • Answer

      Your pulmonary veins carry blood that is richly oxygenated by your lungs to the left atrium of your heart, while most veins carry oxygen-poor blood to the right atrium of your heart.

  2. Why do you think your coronary arteries are called “end circulation” for the heart?

    • Answer

      Your coronary arteries are the only source of blood to your heart. They are your heart’s “end circulation”—and only circulation.

  3. Your heart’s four valves are divided into two categories: atrioventricular valves and semilunar valves. Which valves do you think are atrioventricular? Which valves do you think are semilunar?

    • Answer

      The tricuspid valve and the mitral valve are atrioventricular. They connect the atria and ventricles. The pulmonary valve and aortic valve are semilunar valves. They are shaped like half-moons (semi-lunar).

aorta
Noun

main blood vessel carrying oxygen-rich blood from the heart to all other parts of the body except the lungs.

aortic valve
Noun

heart valve controlling the flow of oxygen-rich blood from the left ventricle of the heart to the aorta.

artery
Noun

blood vessel carrying blood from the left ventricle of the heart to the rest of the body.

atrium
Noun

(plural: atria) upper chamber of the heart that receives blood from veins and forces it into a ventricle (lower chamber).

blood
Noun

fluid pumped by the heart through arteries and veins, delivering nutrients to tissues. In humans, blood consists of plasma in which red blood cells, white blood cells, and platelets are suspended.

chamber
Noun

sealed compartment.

coronary artery
Noun

vessel that supplies blood to the heart.

efficient
Adjective

performing a task with skill and minimal waste.

heart
Noun

vital organ for all animals with a circulatory system, responsible for pumping blood throughout the body.

lung
Noun

organ in an animal that is necessary for breathing.

mitral valve
Noun

heart valve controlling the flow of oxygen-rich blood from the left atrium to the left ventricle.

myocardium
Noun

muscle tissue of the heart.

oxygenate
Verb

to fill with oxygen.

pulmonary artery
Noun

blood vessel carrying oxygen-poor blood from the right ventricle of the heart to the lungs.

pulmonary valve
Noun

heart valve controlling the flow of blood from the right ventricle of the heart to the pulmonary artery, which carries blood from the heart to the lungs.

pulmonary vein
Noun

one of four blood vessels (two for each lung) carrying oxygen-rich blood from the lungs to the left atrium.

septum
Noun

dividing membrane between two cavities or tissues in the body.

tissue
Noun

cells that form a specific function in a living organism.

tricuspid valve
Noun

heart valve controlling the flow of oxygen-poor blood from the right atrium to the right ventricle.

valve
Noun

device used to control the flow of fluid through a passage.

vein
Noun

blood vessel carrying blood to the heart.

vena cava
Noun

one of two large veins (superior vena cava and inferior vena cava) carrying oxygen-poor blood to the right atrium of the heart.

ventricle
Noun

one of two lower chambers of the heart that receive blood from the atria and pump it into arteries.